sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling buggrafted

alb_break_llc() decides whether to break LLC preference during active
load balance. It does so by testing that every runnable fair task on the
source rq prefers its LLC:

	env->src_rq->nr_pref_llc_running == env->src_rq->cfs.h_nr_runnable

But the two counters cover different sets. nr_pref_llc_running is updated
in account_llc_enqueue()/account_llc_dequeue(), next to cfs_rq->nr_queued,
so it follows queued tasks. h_nr_runnable is updated in set_delayed()/
clear_delayed() and drops delay-dequeued tasks.

So under DELAY_DEQUEUE, a preferring task that goes to sleep stays counted
in nr_pref_llc_running while h_nr_runnable falls. The equality then breaks,
alb_break_llc() returns false, and active balance is free to pull a task
off its preferred LLC. Active balance only moves runnable tasks, and this
is the only LLC check it consults: once the stopper runs, LBF_ACTIVE_LB
skips the per-task test in can_migrate_task(). The runnable set is the one
we want.

Fix it on the counter side. A task should be counted in
nr_pref_llc_running exactly while it is both queued on its preferred LLC
(pref_llc_queued) and runnable (!sched_delayed). Define that membership
once in task_pref_llc_runnable(), and adjust the counter only through
pref_llc_running_inc()/pref_llc_running_dec() from the four sites that
change either input: account_llc_enqueue(), account_llc_dequeue(),
set_delayed() and clear_delayed(). Gating every update on the same
predicate keeps the delay, wake and dequeue paths from double-counting
or underflowing; see the comments at those sites for the ordering.

nr_llc_running and sd->llc_counts are not touched and stay on queued
semantics.

Fixes: 714059f79ff0 ("sched/cache: Handle moving single tasks to/from their preferred LLC")
Closes: https://lore.kernel.org/lkml/20260827135000.735138-1-zhanxusheng@xiaomi.com/
Reported-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
Suggested-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Kayra Cizmeci <kayracizmeci@gmail.com>
Cc: <stable@kernel.org> # v7.2.x
Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com

1 files changed, 209 insertions, 0 deletions

diff --git a/include/crypto/sha1.h b/include/crypto/sha1.h
new file mode 100644
index 000000000..4d973e016
--- /dev/null
+++ b/include/crypto/sha1.h
@@ -0,0 +1,209 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Common values for SHA-1 algorithms
+ */
+
+#ifndef _CRYPTO_SHA1_H
+#define _CRYPTO_SHA1_H
+
+#include <linux/types.h>
+
+#define SHA1_DIGEST_SIZE        20
+#define SHA1_BLOCK_SIZE         64
+#define SHA1_STATE_SIZE         offsetof(struct sha1_state, buffer)
+
+#define SHA1_H0		0x67452301UL
+#define SHA1_H1		0xefcdab89UL
+#define SHA1_H2		0x98badcfeUL
+#define SHA1_H3		0x10325476UL
+#define SHA1_H4		0xc3d2e1f0UL
+
+extern const u8 sha1_zero_message_hash[SHA1_DIGEST_SIZE];
+
+struct sha1_state {
+	u32 state[SHA1_DIGEST_SIZE / 4];
+	u64 count;
+	u8 buffer[SHA1_BLOCK_SIZE];
+};
+
+/* State for the SHA-1 compression function */
+struct sha1_block_state {
+	u32 h[SHA1_DIGEST_SIZE / 4];
+};
+
+/**
+ * struct sha1_ctx - Context for hashing a message with SHA-1
+ * @state: the compression function state
+ * @bytecount: number of bytes processed so far
+ * @buf: partial block buffer; bytecount % SHA1_BLOCK_SIZE bytes are valid
+ */
+struct sha1_ctx {
+	struct sha1_block_state state;
+	u64 bytecount;
+	u8 buf[SHA1_BLOCK_SIZE];
+};
+
+/**
+ * sha1_init() - Initialize a SHA-1 context for a new message
+ * @ctx: the context to initialize
+ *
+ * If you don't need incremental computation, consider sha1() instead.
+ *
+ * Context: Any context.
+ */
+void sha1_init(struct sha1_ctx *ctx);
+
+/**
+ * sha1_update() - Update a SHA-1 context with message data
+ * @ctx: the context to update; must have been initialized
+ * @data: the message data
+ * @len: the data length in bytes
+ *
+ * This can be called any number of times.
+ *
+ * Context: Any context.
+ */
+void sha1_update(struct sha1_ctx *ctx, const u8 *data, size_t len);
+
+/**
+ * sha1_final() - Finish computing a SHA-1 message digest
+ * @ctx: the context to finalize; must have been initialized
+ * @out: (output) the resulting SHA-1 message digest
+ *
+ * After finishing, this zeroizes @ctx.  So the caller does not need to do it.
+ *
+ * Context: Any context.
+ */
+void sha1_final(struct sha1_ctx *ctx, u8 out[at_least SHA1_DIGEST_SIZE]);
+
+/**
+ * sha1() - Compute SHA-1 message digest in one shot
+ * @data: the message data
+ * @len: the data length in bytes
+ * @out: (output) the resulting SHA-1 message digest
+ *
+ * Context: Any context.
+ */
+void sha1(const u8 *data, size_t len, u8 out[at_least SHA1_DIGEST_SIZE]);
+
+/**
+ * struct hmac_sha1_key - Prepared key for HMAC-SHA1
+ * @istate: private
+ * @ostate: private
+ */
+struct hmac_sha1_key {
+	struct sha1_block_state istate;
+	struct sha1_block_state ostate;
+};
+
+/**
+ * struct hmac_sha1_ctx - Context for computing HMAC-SHA1 of a message
+ * @sha_ctx: private
+ * @ostate: private
+ */
+struct hmac_sha1_ctx {
+	struct sha1_ctx sha_ctx;
+	struct sha1_block_state ostate;
+};
+
+/**
+ * hmac_sha1_preparekey() - Prepare a key for HMAC-SHA1
+ * @key: (output) the key structure to initialize
+ * @raw_key: the raw HMAC-SHA1 key
+ * @raw_key_len: the key length in bytes.  All key lengths are supported.
+ *
+ * Note: the caller is responsible for zeroizing both the struct hmac_sha1_key
+ * and the raw key once they are no longer needed.
+ *
+ * Context: Any context.
+ */
+void hmac_sha1_preparekey(struct hmac_sha1_key *key,
+			  const u8 *raw_key, size_t raw_key_len);
+
+/**
+ * hmac_sha1_init() - Initialize an HMAC-SHA1 context for a new message
+ * @ctx: (output) the HMAC context to initialize
+ * @key: the prepared HMAC key
+ *
+ * If you don't need incremental computation, consider hmac_sha1() instead.
+ *
+ * Context: Any context.
+ */
+void hmac_sha1_init(struct hmac_sha1_ctx *ctx, const struct hmac_sha1_key *key);
+
+/**
+ * hmac_sha1_init_usingrawkey() - Initialize an HMAC-SHA1 context for a new
+ *				  message, using a raw key
+ * @ctx: (output) the HMAC context to initialize
+ * @raw_key: the raw HMAC-SHA1 key
+ * @raw_key_len: the key length in bytes.  All key lengths are supported.
+ *
+ * If you don't need incremental computation, consider hmac_sha1_usingrawkey()
+ * instead.
+ *
+ * Context: Any context.
+ */
+void hmac_sha1_init_usingrawkey(struct hmac_sha1_ctx *ctx,
+				const u8 *raw_key, size_t raw_key_len);
+
+/**
+ * hmac_sha1_update() - Update an HMAC-SHA1 context with message data
+ * @ctx: the HMAC context to update; must have been initialized
+ * @data: the message data
+ * @data_len: the data length in bytes
+ *
+ * This can be called any number of times.
+ *
+ * Context: Any context.
+ */
+static inline void hmac_sha1_update(struct hmac_sha1_ctx *ctx,
+				    const u8 *data, size_t data_len)
+{
+	sha1_update(&ctx->sha_ctx, data, data_len);
+}
+
+/**
+ * hmac_sha1_final() - Finish computing an HMAC-SHA1 value
+ * @ctx: the HMAC context to finalize; must have been initialized
+ * @out: (output) the resulting HMAC-SHA1 value
+ *
+ * After finishing, this zeroizes @ctx.  So the caller does not need to do it.
+ *
+ * Context: Any context.
+ */
+void hmac_sha1_final(struct hmac_sha1_ctx *ctx,
+		     u8 out[at_least SHA1_DIGEST_SIZE]);
+
+/**
+ * hmac_sha1() - Compute HMAC-SHA1 in one shot, using a prepared key
+ * @key: the prepared HMAC key
+ * @data: the message data
+ * @data_len: the data length in bytes
+ * @out: (output) the resulting HMAC-SHA1 value
+ *
+ * If you're using the key only once, consider using hmac_sha1_usingrawkey().
+ *
+ * Context: Any context.
+ */
+void hmac_sha1(const struct hmac_sha1_key *key,
+	       const u8 *data, size_t data_len,
+	       u8 out[at_least SHA1_DIGEST_SIZE]);
+
+/**
+ * hmac_sha1_usingrawkey() - Compute HMAC-SHA1 in one shot, using a raw key
+ * @raw_key: the raw HMAC-SHA1 key
+ * @raw_key_len: the key length in bytes.  All key lengths are supported.
+ * @data: the message data
+ * @data_len: the data length in bytes
+ * @out: (output) the resulting HMAC-SHA1 value
+ *
+ * If you're using the key multiple times, prefer to use hmac_sha1_preparekey()
+ * followed by multiple calls to hmac_sha1() instead.
+ *
+ * Context: Any context.
+ */
+void hmac_sha1_usingrawkey(const u8 *raw_key, size_t raw_key_len,
+			   const u8 *data, size_t data_len,
+			   u8 out[at_least SHA1_DIGEST_SIZE]);
+
+#endif /* _CRYPTO_SHA1_H */